Serena Williams will not back down from criticism. John Mcenroe will not back down from criticizing. Together, the two stubborn forces promise to create a Tennis feud for the ages. On Tuesday morning, the male star was given an opportunity to back down from the comments he made over the weekend, which were seen as sexist by some. Instead of backing down, however, he doubled down on his comments, allowing the controversy to rage on.

McEnroe keeps the spat going

McEnroe appeared on "CBS This Morning" on Tuesday. He was interviewed by Norah O’Donnell, who asked if the former star would be willing to apologize for his previous comments; he declined that opportunity.

He admitted that he didn't mean to stir controversy with his recent comments about Williams, but doesn't regret them. He did clarify that he believed she was the greatest female tennis player of all-time.

McEnroe did have the chance to give Williams a new ranking on his totem pole. She received a big promotion, from outside the Top 700 to within the Top 5. He placed her right behind Roger Federer, Rafael Nadal, Rod Laver, and Pete Sampras. There has been no response yet from the female tennis star, who may be too busy focusing on having a baby to really care too much about what McEnroe says.

Williams takes the high road

The controversy kicked off earlier in the week during an NPR interview. He was asked if Williams was an all-time great, which he affirmed.

But he refused to drop the qualifier in the statement, which is that she's a woman. When asked to drop the qualifier, McEnroe stated that she wouldn't even rank in the Top 700 of men's players due to the nature of the gender's different games. Clearly, he doesn't have a great deal of knowledge about the famous "Battle of the Sexes," where female Billie Jean King took down male Bobby Riggs.

Williams tried to take the high road when responding to McEnroe's earlier comments. She responded with a series of tweets, first asking McEnroe not to talk about her outside of a factual basis, and then to allow her to focus on her pregnancy. It was a decent enough statement, although a tad awkward, as she added what felt like a sarcastic "good day sir" at the end.

But she does have better things to focus on. She and Reddit co-founder Alex Ohanian are due to have their baby sometime in early September. After that, she'll have the opportunity to step back on the court and prove her latest nemesis wrong.

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